Generally, the present invention is directed to a system and method for measuring, processing and archiving launch vehicle tank subassemblies, (e.g., barrels, skirts, etc.), and is particularly useful in determining supplier tolerance and repeatability capabilities, and in determining the amount of fuel to be contained within the launch vehicle fuel tanks since welds between tank subassemblies (e.g., a skirt welded to a barrel) can result in shrinkage of the overall length between subassemblies.
Launch and other space travel vehicles often include one or more fuel tanks for the storage of an appropriate fuel therein. These fuel tanks include an enclosed structure or a xe2x80x9cpressure vesselxe2x80x9d, as well as structure for interconnecting a given fuel tank with another fuel tank or an engine. Relatively large amounts of fuel are required, and therefore each of the fuel tanks is typically defined by a plurality of fuel tank subassemblies which are appropriately interconnected. One common configuration for fuel tanks of this type which has been employed and which is admitted to be prior art is one in which two xe2x80x9ccombosxe2x80x9d were interconnected by a barrel. Each combo was defined by a skirt which was welded to a dome body. Both ends of the skirt were open and the skirt was of a cylindrical configuration, extending concentrically about and along a central, longitudinal axis of the fuel tank. One end of the dome body was closed and defined by a xe2x80x9cdomedxe2x80x9d surface which was centrally disposed about the central, longitudinal axis of the fuel tank, and further which was typically disposed between the two open ends of the skirt, while its opposite end was open and extended beyond one of the open ends of the skirt for interconnecting the dome body with both the skirt and the barrel. Definition of the open end of the dome body was actually provided by a cylindrical portion which extended from the outer perimeter of the domed surface to the opposite open end concentrically about and along the central, longitudinal axis of the fuel tank. There a generally T-shaped connector of sorts extended radially outwardly relative to the central, longitudinal axis of the fuel tank (i.e., the bottom xe2x80x9clegxe2x80x9d of the T-shaped connector extended at least generally outwardly and away from the cylindrical portion of the dome body). One of the two xe2x80x9cupper legsxe2x80x9d of the T-shaped connector butted up against one of the ends of the skirt and was welded thereto, while the other of the xe2x80x9cupper legsxe2x80x9d of the T-shaped connector butted up against one of the two open ends of the cylindrical barrel and was welded thereto.
One known prior art method for assembling fuel tanks from the above-noted subassemblies used a system having a headstock and a longitudinally displaced tailstock which each functioned as a chuck of sorts to retain/hold a fuel tank subassembly. A track extended longitudinally between this headstock and tailstock and along which both the headstock and tailstock could axially move. A carriage of sorts was also movably interconnected with this track and had both a saw and a router attached thereto. Movement of this carriage was controlled by an appropriate operative interconnection with a drive assembly, which in turn was manually controlled by appropriate personnel. Welds between adjoining fuel tank subassemblies were provided by a welding assembly which was associated with the system as well.
Assemblage of a fuel tank using the above-noted system and in accordance with an admitted prior art protocol first entailed attaching one of the ends of a first skirt to the headstock. Operations personnel then placed a mark or the like a predetermined distance from the end of the skirt engaged by the headstock through use of a calibrated measuring tape, stick, or other item of fixed length. This xe2x80x9cpredetermined distancexe2x80x9d corresponded with the length of the skirt as set forth on the relevant engineering drawing. Thereafter, the carriage was moved longitudinally along the track to bring the router into contact with the free end of the skirt through manual control of the longitudinal position of the carriage (and thereby the router) by appropriate personnel, and by what is commonly referred to as a xe2x80x9csneaking upxe2x80x9d operation. That is, the carriage was moved to a certain longitudinal position and the skirt was rotated to see if the router engaged any portion thereof. If there was no engagement, the operator would try to estimate how much the router had to be moved longitudinally by visual analysis, and the carriage would then be moved longitudinally this amount to again check and see if the router would engage any portion of the skirt during rotation thereof. This was repeated until engagement was established.
Routering operations were affected on the noted end of the skirt by using relative rotational motion between the skirt and the router. Typically this involved rotating the skirt via rotation of the headstock. Furthermore, the router was moved longitudinally toward the headstock by longitudinal movement of the carriage along the track toward the headstock via the carriage drive assembly until the router reached the above-noted mark and which was determined through visual inspection by appropriate personnel. Further longitudinal movements of the carriage toward the headstock were then manually terminated by the appropriate personnel. Visual inspection of the machined end of the skirt was then undertaken by appropriate personnel. If any portion of the end of the skirt was visually determined to lack router markings, it was assumed that the skirt did not meet the minimum length requirement of the skirt for the subject fuel tank. Discussions were then typically undertaken with relevant personnel to determine how to best proceed (i.e., recover). If the entire circumference of the end of the skirt was determined to have router markings thereon through the noted visual inspection by appropriate personnel, appropriate personnel manually measured the length of the skirt at one radial location and then manually recorded this information in a log book.
The free end of one dome body was attached to the tailstock either before or after prepping the end of the skirt in the above-noted manner. More specifically, the free end of that upper leg of the above-noted T-shaped connector which was to interface with the barrel was engaged by the tailstock. Advancement of the tailstock longitudinally toward the headstock was then undertaken to position the free end of the other upper leg of the T-shaped connector in abutting engagement with the end of the skirt which was prepped in the above-noted manner. A circumferential weld was then made between the skirt and the dome at this butt joint. The resulting structure was again commonly referred to as a combo. The tailstock then released the dome body and proceeded longitudinally away from the headstock for preparation of a barrel for attachment to the combos.
Only one of the upper legs of the T-shaped connector on the free end of the dome body thereby remained after pursuing the protocol thus far described. Actions were then undertaken to prepare the free end of this remaining leg of the T-shaped connector of the dome body for attachment to one of the ends of the open-ended, cylindrical barrel. The carriage would be moved to a certain longitudinal position for sawing a section off of the subject leg of the T-shaped connector through manual operator control of the longitudinal position of the carriage relative to the dome body. The specified length of the combo would be known from the corresponding engineering drawing(s) and was measured from the end of the skirt engaged by the headstock. A mark was placed at this longitudinal position on the dome body in generally the same manner set forth above in relation to the skirt. Operations personnel would manually control longitudinal movement of the carriage (and thereby the saw) to place the saw in the desired longitudinal position for producing a circumferential cut about the entire perimeter of the remaining free leg of the T-shaped connector on the free end of the dome body (using relative rotational movement between the saw and dome body). This xe2x80x9cdesired longitudinal positionxe2x80x9d was one which was slightly beyond the location of the noted mark (i.e., further from the headstock) since routering operations were done after these sawing operations. Routering operations were conducted on the subject end of the dome body generally in the manner discussed above in relation to the skirt. Measurement of the length of the combo was manually made by operations personnel (the distance between the end of the skirt mounted on the headstock and the free end of the remaining free leg of the T-shaped connector defining the free end of the dome body) upon completion of this routering, and this value was manually recorded in a log book by appropriate personnel. This combo was then removed from the headstock, and another combo was built in the same manner as the foregoing.
The barrel commonly used in prior art fuel tank designs, like the skirt, was an open-ended cylinder having a pair of longitudinally spaced free and open ends as noted. One of these ends was attached to the tailstock, and the carriage was then longitudinally moved to position the saw thereon at a certain longitudinal location proximate the opposite end through manual control of the drive assembly by appropriate personnel. Typically operations personnel would manually measure in a certain distance from this end of the barrel (e.g., 2 or 3 inches) and place a mark thereat. Operations personnel would then manually control the longitudinal position of the carriage to dispose the saw just beyond this location (i.e., closer to the free open end opposite that engaged by the tailstock). Relative rotational movement between the barrel and the saw was then undertaken to produce a circumferential cut on the barrel, typically by rotating the barrel through rotation of the tailstock. Thereafter, this end of the barrel was also routered through operations personnel manually controlling the longitudinal position of the carriage relative to the tailstock and through relative rotational motion between the barrel and the router (typically via rotation of the tailstock), and further generally in the manner discussed above in relation to the skirt, to obtain the desired length.
Advancement of the tailstock with the barrel attached thereto longitudinally toward the headstock with one of the combos attached thereto was then made to dispose the xe2x80x9cpreppedxe2x80x9d end of the barrel in abutting engagement with the xe2x80x9cpreppedxe2x80x9d end of the remaining free upper leg of the T-shaped connector on the end of the dome body of the combo currently attached to the headstock. Welding operations were then initiated to create a circumferential weld between this combo and the barrel. Thereafter, the barrel was released by the tailstock and its remaining free end was prepared for attachment to the other combo which was previously assembled and which could now be attached to the tailstock. In this regard, a mark was placed on the barrel a predetermined length from the end of the skirt engaged by the headstock, and thereafter sawing and routering operations were undertaken generally in the manner discussed above to obtain the desired length for the combo and barrel interconnected therewith. Appropriate personnel would then manually measure the end length of the combo with the barrel attached thereto and manually record the same in a log book. After having mounted the previously formed combo in the tailstock and longitudinally advancing the same toward the barrel to position the remaining free end of the barrel in abutting engagement with the prepped end of the remaining free upper leg of the T-shaped connector on the free end of the dome body of the second combo, welding operations were initiated to complete the definition of the fuel tank.
The present invention is particularly suited to the assembly of a fuel tank for a launch or other space travel vehicle from multiple fuel tank subassemblies. Although the present invention will be discussed with regard to this particular application, the principles presented herein are applicable to the assembly of any type of pressure vessel from multiple subassemblies.
A first aspect of the present invention is generally directed to the assembly of an enclosed fuel tank for a space travel vessel from at least first and second fuel tank subassemblies. Each of these first and second fuel tank subassemblies have first and second longitudinally spaced ends. Preparation of the first fuel tank subassembly for attachment to the second fuel tank subassembly includes measuring the length of the first fuel tank subassembly between its two ends and then recording the same in a first instance. As such, this will be referred to as a xe2x80x9cfirst length measurement.xe2x80x9d Measuring the first fuel tank subassembly at this time may be used to evaluate a supplier""s compliance with engineering specifications provided in relation to the first fuel tank subassembly, and which may be augmented by having these measurements from a common supplier of a plurality of these same first fuel tank subassemblies. After this first length measurement is obtained, at least some type of machining operation is executed on the first fuel tank subassembly at a location which may be characterized as being longitudinally spaced from its first end. Representative machining operations include sawing and routering operations which would be executed on the first fuel tank subassembly at a location spaced from the first end, commonly at least generally proximate the second end (e.g., sawing operations typically being done at a location which is longitudinally spaced from the second end a relatively small distance, and routering operations being done on the second end itself). In any case, the subject machining of the first fuel tank subassembly defines a new second end therefore since the length of the first fuel tank subassembly is modified from its original state (e.g., as received from the supplier). In this regard, after the machining operation, the length of the first fuel tank subassembly between its longitudinally spaced ends is once again measured. Since this is the second instance of the measurement of the length of the first fuel tank subassembly, such will be referred to as a xe2x80x9csecond length measurement.xe2x80x9d This second length measurement is also recorded. Measuring the first fuel tank subassembly at this time may be used to evaluate the accuracy of the machining operation which was just done in relation to the first fuel tank subassembly, and which may be augmented by having these measurements from a plurality of similar machining operations conducted on a plurality of the same first fuel tank subassemblies. At least sometime after obtaining the second length measurement of the first fuel tank subassembly, the newly defined second end of the first fuel tank subassembly is attached (e.g., welded) to one of the ends of the second fuel tank subassembly. Preferably this second fuel tank subassembly has been xe2x80x9cpreparedxe2x80x9d for attachment to the first fuel tank subassembly in the same general manner noted above in relation to the first fuel tank subassembly (e.g., measuring length before and after each machining operation).
Various refinements exist of the features noted in relation to the subject first aspect of the present invention. Further features may also be incorporated in the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Measurement of the length of a particular fuel tank subassembly may entail longitudinally advancing a measuring device along the subject fuel tank subassembly. First the measuring device may be longitudinally advanced to dispose the measuring device past the second end of the same such that the second end is actually then longitudinally disposed between the measuring device and its corresponding first end of the subject fuel tank subassembly. The measuring device may then be longitudinally advanced back toward the second end of the subject fuel tank subassembly (in the opposite direction to that referred to above) until the measuring device engages the second end of the subject fuel tank subassembly. Positioning the measuring device at a longitudinal location corresponding with the longitudinal position of the first end of the subject fuel tank subassembly before initiating the above-described movements of the measuring device may define a first position (which may entail a longitudinal advancement of the measuring device to this location as well), and the position of the measuring device upon termination of its motion by its engagement with the second end of the subject fuel tank subassembly may define a second position. The length of the subject fuel tank subassembly may be derived from these two positions.
Actions may be undertaken to increase the likelihood that the measuring device will actually contact the second end of the subject fuel tank subassembly when moved longitudinally back towards the same in the longitudinal direction. Longitudinal movement of the measuring device toward the second end of the subject fuel tank subassembly, when coming from the direction of the first end of the subject fuel tank subassembly, may be terminated before actually disposing the measuring device at a longitudinal location which is beyond the longitudinal position of the second end of the subject fuel tank subassembly. The measuring device then may be directed at least generally laterally or toward the subject fuel tank subassembly until contacting the same (e.g., to xe2x80x9chitxe2x80x9d the body of the subject fuel tank subassembly or its outer diameter), at which time further lateral movement of the measuring device in this direction may be terminated. This serves to determine the position in space of the outer wall of the subject fuel tank subassembly at its current radial position, which may be defined relative to a reference axis about which the subject fuel tank subassembly assembly is disposed and extends longitudinally along. This lateral position of the measuring device is noted, the measuring device is laterally retracted away from the body of the subject fuel tank subassembly a certain amount, and the measuring device is then longitudinally advanced so as to be disposed longitudinally beyond the second end of the subject fuel tank subassembly. Then the measuring device is laterally advanced at least generally toward the reference axis to a position such that when it is longitudinally advanced back toward the second end of the subject fuel tank subassembly, it will contact the same so that the length measurement may be obtained (e.g., the amount that the measuring device was retracted away from the outer diameter of the subject fuel tank subassembly, plus possibly an amount relating to the configuration/dimension of a sensing surface of the measuring device).
The length of a particular fuel tank subassembly before any machining thereof in accordance with the above may be measured at each of plurality of radially spaced locations (i.e., to check for length variations at different locations between the first and second ends). One way to affect these measurements would be to rotate the subject fuel tank subassembly relative to a measuring device, to stop this relative rotational movement at each of a plurality of radially spaced locations, and then obtain the length measurement in accordance with the foregoing. What is considered as xe2x80x9cradially spacedxe2x80x9d may be illustrated by the case of a fuel tank subassembly which includes at least a cylindrical portion. Assume that the measuring device is disposed at the 0 degree location of the cylindrical portion and relative to an axis about which the cylindrical portion is disposed. The length may be measured at this 0 degree location. Thereafter relative rotational motion may be employed to rotate the cylindrical portion 15 degrees about the noted axis, and another length measurement may again proceed in accordance with the foregoing. Any desired radial spacing may of course be employed.
Obtaining a plurality of first length measurements through these plurality of radially spaced locations may be used to identify a minimum length and a maximum length of the subject fuel tank subassembly. This in turn may be used to evaluate whether the subject fuel tank subassembly meets engineering specifications before being attached to the second fuel tank subassembly. That is, a certain length (including those within a certain tolerance) may be required for a first fuel tank subassembly prior to attaching the same to a second fuel tank subassembly. If the minimum length of the first fuel tank subassembly is less than the length set out in the engineering specifications, the assembly process of the fuel tank may be terminated to address how the assembly thereof should then proceed.
The subject machining operations may be affected by longitudinally advancing the required machining tool to a predetermined longitudinal location. For instance, this predetermined longitudinal location may be a fixed distance from the first end of the first fuel tank subassembly. Obtaining the second length measurement may then be used to evaluate the accuracy with which the machine tool was placed relative to the longitudinal extent of the first fuel tank subassembly. One particularly desirable implementation is to include the device which is used in the measurement of the length of the first fuel tank subassembly on a common carriage with a machine tool that does the noted machining operation.
A second aspect of the present invention is embodied in a system for assembling an enclosed fuel tank for a launch or other space travel vehicle from at least first and second fuel tank subassemblies. Each of these first and second fuel tank subassemblies have first and second longitudinally spaced ends. A pair of longitudinally spaced first and second chucks or the like are provided which function to engage/hold certain subassemblies of the fuel tank during the assembly thereof. For instance during the assembly of a given fuel tank, the first end of the first fuel tank subassembly may be engaged by the first chuck in a manner such that the first fuel tank subassembly extends away therefrom toward the second chuck, and the first end of the second fuel tank subassembly may be engaged by the second chuck in a manner such that the second fuel tank subassembly extends way therefrom toward the first chuck. Appropriate supports may be provided between the noted pair of longitudinally spaced first and second chucks to bear at least part of a load of the overlying subassembly engaged thereby.
The system of the second aspect of the present invention further includes a longitudinally extending guide assembly (e.g., a track) which is disposed at least substantially parallel with the longitudinal extent of the subassemblies when mounted on the noted chucks. Typically this track will be laterally offset from the central, longitudinal axis of the fuel tank subassemblies when mounted on or interconnected with a given chuck, but such need not be the case. A first carriage is movably interconnected with this guide assembly. Interconnected with this first carriage is a drive assembly for longitudinally moving the first carriage along the guide assembly to dispose the first carriage at different longitudinal locations relative to a fuel tank subassembly mounted on the noted chuck(s). Other motions may be affected by the drive assembly as well, and such may be defined by one or more separate drives or motors which would then collectively define a drive assembly.
Certain devices are attached to the first carriage in relation to the assembly of the fuel tank in accordance with the subject second aspect. Both a first machine tool (e.g., saw, router) and a fuel tank/fuel tank subassembly measuring device are both attached to the first carriage. Other devices may be attached to the first carriage as well, such as other machine tools used in the assembly of the fuel tank. These machine tools which are attached to the first carriage are used to prepare the ends of the various fuel tank subassemblies for interconnection with another fuel tank subassembly. In this regard, the system of the second aspect of the present invention further includes a first welding assembly for joining the various fuel tank subassemblies together.
Various refinements exist of the features noted in relation to the subject second aspect of the present invention. Further features may also be incorporated in the subject second aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Information on the length of the various fuel tank subassemblies used to define the fuel tank for the space travel vessel are preferably automatically recorded from signals sent from the measuring device. For instance, a computer-readable storage medium may be operatively interconnected with the measuring device. One desirable implementation is too operatively interconnect an appropriate computer with both the drive assembly and the measuring device to control the longitudinal movement of the first carriage along the guide assembly and to monitor the longitudinal location of the first carriage via the measuring device. Therefore, the drive assembly and the measuring device are effectively operatively interconnected as well.
Automatic recordation of information to the computer-readable storage medium from the measuring device provides various advantages. Further advantages may be realized by including a certain structure for the storage of information thereon. Preferably all information recorded on the computer-readable storage medium is associated on a fuel tank-by-fuel tank basis, and further on a fuel tank subassembly-by-fuel tank subassembly basis as well. This provides the history of each fuel tank assembled by the system of the second aspect of the present invention. Certain information is also preferably recorded on the computer-readable storage medium for each fuel tank subassembly of a given fuel tank assembled through the second aspect. Preferably the measuring device is used to measure the length of each fuel tank subassembly before having any of its ends prepared for attachment to another fuel tank subassembly (e.g., the length of the fuel tank subassembly as received from the supplier). Furthermore, preferably the measuring device is used to measure the length of each fuel tank subassembly after each machining operation executed thereon by the system of the second aspect. This would include, but is not limited to, after any sawing operation which removes an end section from a given fuel tank subassembly, as well as a routering operation which trims at least a portion of an end of a fuel tank subassembly. Such may be used to monitor the control of the machining operations being provided by the computer (e.g., the control of the longitudinal position of the same). The measuring device also may be used to measure the length of any intermediate structure in the assembly of the fuel tank, such as the interconnection of two or more fuel tank subassemblies.
A third aspect of the present invention is directed to the assembly of an enclosed fuel tank for a launch or other space travel vehicle from at least first and second fuel tank subassemblies. Each of these first and second fuel tank subassemblies have first and second longitudinally spaced ends. The length of the first fuel tank subassembly between such ends is measured at a plurality of radially spaced locations thereon. Consider the case where the first fuel tank subassembly is cylindrical or at least has a cylindrical end. xe2x80x9cRadially spacedxe2x80x9d in this context means a location on a perimeter of the fuel tank subassembly relative to an axis about which this cylinder or cylindrical portion is disposed. After these measurements are taken, a first machining operation is executed on the first fuel tank subassembly, such as a routering of one of the ends of the first fuel tank subassembly. Thereafter, the first fuel tank subassembly may be attached to the second fuel tank subassembly, such as by welding.
Various refinements exist of the features noted in relation to the subject third aspect of the present invention. Further features may also be incorporated in the subject third aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. Length measurements may be made in accordance with that noted above in relation to the first aspect of the present invention. One way to affect the above-noted measurements would be to rotate the subject fuel tank subassembly relative to a measuring device, to stop the relative rotational movement at each of a plurality of radially spaced locations, and then obtain the length measurement in accordance with the foregoing. Obtaining a plurality of first length measurements through these plurality of radially spaced locations may be used to identify a minimum length and a maximum length of the subject fuel tank subassembly. This in turn may be used to evaluate whether the subject fuel tank subassembly meets engineering specifications before being attached to the second fuel tank subassembly. That is, a certain length (including those within a certain tolerance) may be required for a first fuel tank subassembly prior to attaching the same to a second fuel tank subassembly. If the minimum length of the first fuel tank subassembly is less than the length set out in the engineering specifications, the assembly process of the fuel tank may be terminated to address how the assembly should then proceed. These measurements may also be used to monitor the quality of first fuel tank subassemblies being provided by a particular supplier.